Changes in total lipids, fatty acid profiles and cytoplasmic leakage in germinating cowpea [Vigna unguiculata (l.) Walp] seeds

Cowpea [Vigna unguiculata (L.) Walp.] seeds were germinated for 72 hr at varying regimes with 12 hr. increment. Changes in fresh weight, percent radicle emergence, seed and seedling length, and cytoplasmic leakage during this germination period were examined. Leakage of substances absorbing UV light at 280 nm was observed to be at rapid rate during the first 12 to 24 hr of germination. Further significant increase in the amount of leakage was observed only after 72 hr of germination, but was not associated with high inhibition rates. Total lipid content and analysis of fatty acid composition during this 72-hr germination period were determined. Germinating seeds exhibited relatively lower levels of total lipids ranging from 1.20 to 1.48 percent compared to 1.58 percent in ungerminated seeds. The differences in the total lipid levels were, however, statistically insignificant. Gas chromatographic analysis revealed differences in the fatty acid profiles of total lipids at various germination regimes. The following fatty acids and their respective proportion were detected in total lipid extracts from ungerminated seeds: 0.07 percent myristic acid, 1.47 percent palmitic acid, 3.54 percent 18-carbon fatty acids, 0.26 percent arachidic acid and 0.33 percent behenic acid. Throughout the 72-hr germination period, palmitic acid and 18-carbon fatty acids were detected in large proportions while myristic, arachidic and behenic acids were detected in trace amounts. However, the levels of these fatty acids were observed to decline within the first 12 hr of inhibition. The varying proportions of fatty acids from extracts of 24-hr to 48-hr seedlings reflect that metabolism of these particular fatty acids occurred at different rates during germination. Increased amounts of palmitic acid, 18-carbon fatty acids and arachidic acid were detected from extracts of 72-hr seedlings. These observations revealed that germination of cowpea seeds undergoes a triphasic process of change